This invention relates to electronic valve control systems and more particularly to electronic throttle control systems for internal combustion engines with gear mechanisms having reduced friction and wear.
Valve assemblies for engines and related systems typically utilize rotatable valve members in fluid flow passageways to assist in regulating fluid flow through them. For example, throttle valve members are positioned in the air induction passageways in internal combustion engines. The valve assemblies are controlled either mechanically or electronically and utilize a mechanism which directly operates the valve member.
For electronic throttle control systems, it is desirable to have a failsafe mechanism or system which activates the throttle valve in the event that the electronic control or electronic system of the vehicle fails. There are several known electronic throttle control systems which utilize failsafe mechanisms for closing the throttle valve or moving it to a slightly open position in the event of an electronic failure in the vehicle. One of these systems is shown, for example, in the Applicant""s co-pending patent application Ser. No. 09/438,122, filed Nov. 10, 1999, (FGT 199-0418), the disclosure which is hereby incorporated by reference herein.
It would be desirable to have an electronic valve control system with an improved failsafe or limp-home mechanism and which optimizes the operation and positions of the gear mechanism and gear components in order to minimize friction and wear.
The present invention provides an electronic throttle control assembly having a housing with a gear train and throttle valve mechanism. A throttle plate is positioned on a throttle shaft and the plate and shaft are positioned in the engine or air induction passageway, such that the throttle plate regulates airflow into the engine. A cover member enclosing the gear train contains a motor with a spur gear.
The operation of the throttle valve is accomplished through the gear train assembly which is driven by the motor. The motor is regulated by the electronic control unit of the vehicle which in turn is responsive to the input of the vehicle operator or driver. A throttle position sensor responsive to the rotation of the throttle shaft feeds back the position of the throttle plate to the electronic control unit.
In the operation of the throttle valve, a gear connected to the motor operates an intermediate gear (or idler gear), which in turn operates a sector gear which is connected to the throttle body shaft. The sector gear is biased by a spring member toward the closed position of the throttle valve. As a failsafe mechanism, a spring-biased plunger member is attached to the housing and positioned to interrupt operation of the sector gear in the event of an electronic failure and prevent the throttle valve from closing completely. At the failsafe position, the vehicle can still be operated, although at a reduced capacity. This allows the driver to xe2x80x9climp-home.xe2x80x9d
If the throttle valve is in its closed position when an electronic failure occurs, the spring-biased plunger member acts on the sector gear to open the throttle valve slightly to the failsafe position.
In order to minimize friction and wear on the sector gear which are created by contact of the gear with the plunger member of the default mechanism, the components are positioned such that the activation surface of the sector gear is perpendicular to the longitudinal axis of the plunger member at a position approximately midway in the default range of travel of the plunger and sector gear. This minimizes the sliding contact and friction between the plunger member and sector gear surface and as a result reduces friction and enhances performance of the default mechanism. This also reduces wear on the sector gear which is typically constructed of a composite material.
Other features and advantages of the present invention will become apparent from the following description of the invention, particularly when viewed in accordance with the accompanying drawings and appended claims.